Sounds very interesting.
What do you think of the XHP70.2?
Is it too floody?
(My brightest flashlight has an XHP70.2 and I'm a bit of a lumen wh0re.)
XHP70.2 is way too floody for this use case. Needs to be throwy - at least to S2+ with 5A driver or original FW1A standards.
I don't know emitters that well.
Which single emitter is the brightest, and is also quite throwy? (and also doesn't create a ton of heat.)
For light painting purposes, the light has to get as much light as possible through either a 20mm or 25mm aperture in a (flashlight to light painting tool) cone shaped connector, or sit within a 29mm tube depending on the light painting system. Thus peak beam intensity is possibly more important than lumens. I’ve had the best results with XHP35 in the Klarus XT2CR, XP-L HI in FW1A/S2+/SP31 V2.0, CSLNM1.TG in S2+, and SST-40 in KR1. Sadly the KR1 is too big for one light painting system (which has a max diameter of 28mm), and due to the head size most of the lumens in the spill beam are lost in the cone shaped connectors. A KR1 like light but in 25mm (ish) 18650 tube format would be perfect.
A link to my flashlight buying guide for light painting is in my signature. It’s about to get a re-write in the next few weeks, with some lights added and others removed. Now a 1x21700 format XHP70.2 flooder that could sustain 2,000 lumens would also float my boat (the max is currently around 1,500lm in the Convoy M21D, Thrunite T2, and Zebralight SC700D) for illumination purposes, but that’s a whole different thread.
Size matters for most people. I knew the fw1a would be my primary carry for a long time when it was first announced. If it’s going to be the size of an S2+ then it’s not really going to deal with heat any better than the fw1a now. A good bit of what made the S2+ so popular is the reliability. Try to put a tube in it and most people aren’t going to buy in.
The S2+ can sustain approx. double the lumens of the FW1A, so it has much better heat handling. There are plenty of reliable lights with inner tubes - Noctigon KR1, KR4, Klarus XT2CR, XT11GT (after gen1), etc. Get the design right and the inner tube isn’t a problem.
It sounds a bit like wishing for incompatible aspects mashed into one light.
Compact + throwy
Compact + on board charging
On board charging + inner tube
Compact + on board charging + good heat dissipation
You might be able to mix 1 or 2 aspects but not all of them
I don’t think it’s too incompatible. Compact and throwy (for EDC size) - plenty of lights manage that - original FW1A, XT2CR, even the S2+ with some emitters. On-board charging is optional, didn’t know it was an issue with inner tube, but regarding size it only adds to length, not width if well designed.
And if all of this is too difficult, just an S2+ with the Biscotti/12-Group alternating frequency strobe reverted back to constant frequency would solve the lack of budget lights suitable for light painting issue, but sadly Simon hasn’t listened to that request.
So really, a modified driver for either the s2+ or fw1a or xt2cr would satisfy most of your want list…?
Ideally it would run Anduril for adjustable strobe frequency, which would require an inner tube for a tail e-switch. But to some extent I’m looking for a Convoy S2+ like light with Anduril, or a slimmer KR1.
How about a modified kr4 - remove quad, install single emitter 
I’m suggesting a production light, not a mod. There are quite a few excellent >$100 lights for light painters, but nothing decent below $50 that fits all systems. The KR4 is 1mm too wide at 29mm, but if it was 1mm narrower and had a single emitter it would be perfect.
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I recall seeing test results with the temperature calibration cranked up to 60C [EDIT zeroair was measuring 38C external in the link below] and 600 lumens sustained with a FW1A. I don’t have mine cranked up that high but I’ll compare the fw1a and S2+ (biscotti) both with a SST4000k. Visual with an infrared thermometer and the same batteries. I predict similar output and temperatures at 5 and 10 minutes. Do you know if the light dancing tubes help or hurt heat dissipation?
That’s not a like for like test though. With my FW1A XP-L HI 6500k calibrated and set to 55C (which I think is the same as the S2+ and around “real world” comfortable holding limits anyway) it is at approx. 250lm at 10 mins. With a 90CRI LH351D 5700k in a 5A/12 group driver S2+ it is running at approx. 500lm at 10 minutes. The S2+ has surprisingly good thermal mass and handling for it’s class. Interestingly though, the FW3X with Lume1 driver seems to be able to sustain much higher lumens than the FW3A.
Not sure why it ‘needs’ to be a production light but okay. Good luck with it 
- I have lots of light painters asking me for a good budget light, and there aren’t any.
- Tail switch 18650 tube lights are hugely popular with flashlight enthusiasts and muggles, and yet there isn’t a decent one with Anduril.
Anyway, it seems there isn’t much interest going by this thread.
The more you explain it the more it makes sense but like you said there doesn’t appear to be much interest in this thread
Maybe this thread isn't that popular because the flashlight is being made for light painters, and most people on BLF don't do light painting.